Numerous clamps are commercially available for clamping the outer diameter of hoses, pipes and the like. Such clamps typically include a clamp band that is maintained in a circular arrangement with its opposite ends overlapping each other in order to encircle the outer diameter of the hose. Such clamps further include a tightening device (usually a worm gear having a threaded screw that mates with slots formed in the clamping band) for reducing or expanding the outer diameter of the band, thereby respectively tightening or loosening the band around the hose.
A particular problem encountered with such clamps is spontaneous loosening. For instance, many of these clamps receive post assembly washing and/or plating operations which agitate the clamps and induce the clamping bands and worm gear to loosen. Moreover, such clamps are often shipped as part of a preliminary assembly and are loosely fit over the ends of hoses, air ducts and the like prior to shipment. These clamps are subjected to shaking and rattling during shipment, and this can result in undesirable loosening of the worm gear. The loosened clamps often run afoul of the strict open-diameter shipping tolerances which are imposed by customers and industry standards. Moreover, the clamps may loosen beyond a "full-open" (or maximum diameter) position. Should the clamp be inadvertently opened beyond the "full-open" diameter, the worm gear will disengage and the clamping band will lose its circular arrangement. An inordinate amount of time must be spent threading the band back through the worm gear to regain the circular form and intended diameter.
The quality requirements at the OEM level have become so stringent that assembly plants will now often reject entire shipments for a couple of disengaged clamps. Of those clamps which do reach the consumer intact, many are returned for OEM repair or replacement after having been disengaged by the consumers.
As a result, certain safeguards have been proposed to avoid spontaneous loosening and disengagement. Such safeguards generally involve increasing the resistance of the worm gear. Unfortunately, this also renders the worm gear more difficult to tighten, and this can run afoul of the low free running torque specifications which are likewise imposed by consumers and industry standard. These specifications essentially dictate that the worm gears have nearly zero turning resistance.
Another common solution comes in the form of tabs formed in one of the clamping bands which engage the worm gear housing to form a structural assembly. Such arrangements can be found by reference to U.S. Pat. Nos.: 2,910,758 issued to Arthur; 2,571,659 issued to Bergstrom; 3,303,544 issued to Nigon; 3,521,334 issued to Bergstrom; 4,237,588 issued to Rasmussen et al.; 3,950,830 issued to Duprez; and 4,286,361 issued to Mackenzie.
The above-referenced patents provide a solution to ultimate disengagement of the worm gear. Conversely, U.S. Pat. No. 4,637,100 issued to Ishihata shows clamping bands with a mating tab and slot arrangement to prevent over-tightening of the band. Regardless, these and other known locking tabs or detent arrangements provide an immutable engagement. The particular diameter at which the lock engages cannot be adjusted or easily changed. None of the prior art locking arrangements is capable of maintaining a selectable fixed open-diameter for shipping purposes or otherwise without creating excessive resistance to turning of the worm gear.